Theoretical thermal efficiencies of ideal, supercharged and gasoline engine cycles

Abstract

This paper updated the perception of theoretical thermal efficiencies of reciprocating engine cycles by the analysis of six ideal cycles (Diesel, Joule-Brayton, Otto, Atkinson, Sabathe and Song). It was theoretically elucidated that more available energy remains in exhaust gas at higher load than at lower one, testifying that the exhaust waster energy recovery is more important at higher load than at lower one. A supercharged cycle was theoretically demonstrated to have lower thermal efficiency than its counterpart naturally-aspirated one, while supercharged engines had been always considered to have higher thermal efficiency. The thermal efficiencies of gasoline engines were first derived, testifying that a homogeneous spark-ignition gasoline engine at part-load has less thermal efficiency than its corresponding Otto cycle and can achieve a higher thermal efficiency by retarding (or advancing) inlet valve closing than by throttling intake flow.